Purification of liquid hydrocarbons



Sept. 23, l193i). l?- s. THoLE Er AL- 1,776,340

l BURIFIGAHON 0F LIQUID HYDROGARBONS Filed Nov. 6, 1924 Fig.l.

Patented Sept. 23, 1930 UNITED STATES PATENT OFFICE* FERDINAND BERN-ARDTHOLE IAN D STEPHEN THOMAS CARD, OF SNBUB'Y-ON-THAHES, ENGLAND, ASSIGNORS TO ANGLO-PERSIAN OIL COMRANY, LIMITED, OF LONDON,

.ENGLAND PURIFICATION OF LIQUID HYDBOCARBONS Application ledl November 6, 1924, Serial No. 748,267, and 1n Great Britain January 1.1, 19M.

This invention relates to the treatment of liquid hydrocarbons for the removal therefrom of sulphur compounds such as organicl sulphides, poly-sulphides and hydro-sul- 5 phides they may contain.

' The invent-ion specifically relates to the use ofhypochlorite solutions such as sodium or calcium hypochlorite for the purpose.

In the use of such solutions .the sulphur compounds contained in the oil are oxidized and the bodies produced readily pass into and are removed with the lye, but it has been found necessary to employ a slight excess of free alkali for the principal purpose of iny hibiting chlorination of the hydrocarbons and of stabilizing the solution so as to inhibit decomposition during storage. This .was rendered necessary owing to theinstability of such hypochlorite solutions without such a slight excess of free alkali The present invention is basedupon the discovery that .the reaction may be accelerated vand the-hypochlorite solution rendered reactive by the reduction in the content of free alkali immediately before the use of the hypochlorite solution or during the treatment, wherebythe solution is to a substantial ex'- tent de-stabilized but under such conditions that the destabilizer is uniformly distributed 8o so that there may be no localv excess of acid, particularly'of strong acid, such` as is very liableto occur if mineral acid is employed for this purpose and which is apt to lead to the spontaneous decomposition of the whole batch. f l

According to the'invention carbon-dioxide is used and is admitted into thevessel in which the treatment is carried out through pipes advantageously mounted at the bot-tom ofthe vessel, means being providedor em-l ployed for stirring the liquids in the treatment to ensure the uniform distribution of the gas andto ensure the necessary intimate admlxture of the hypochlorite solution with the oil, the carbon-dioxide being introduced in such quantity that the content of free caustic soda is reduced practically tozero; or instead of carbon-dioxide asolution'of a metallic salt,'which by reaction with the free alkali '50 precipitates insoluble hydroxides, is' em- 'special plant is requiredl loyed such for example as ferrous sulphate, erric sulphate, ferrie chloride, sulphate magnesium sulphate and zinc sulphate. Such a salt is advantageously introuced into the solution of hypochlorite inthe condition of a solution and is uniformly 'distributed therein, its effect being the same as the addition of carbon dioxide in that by reduction of the concentration of hydroxyl ions, the free alkali is destroyed.

As a practical application indicating the effect of the treatment, the following example ma be given:

\ l n 500 cc. of a sulphur-containin oil being stirred with 130 cc. of 0.382 sodium lhypochlorite containing v1.1 gm. caustic soda per litre,- that is to say with an excess of caustic sodaf to render the solution of hypochlorite manganese suiiiciently stable to be stored, 34.5% of the l hypochloritewas found to have been used up in ten minutes, whereas when the same treatment was carried out with the addition of .19 gms. of ferrie sulphate, 79% of the hypochlorite was used up yin the same period. It will be understood that such an amount of ferrie sulphate consumed .116 gm. of free caustic soda, so that thus .the free alkali content would have been reduced from .143 gm.

to .027 gm. If the quantity of ferrie sulphate added is sufficient to remove the last trace of free alkali under the conditions hereinbefore described, the activity of the hypochlorite is further increased.

The following example demonstrates the effect secured in the use of carbon dioxide.

500 cc. of a sulphur containing oil was stirred with 200 cc. of sodium hypochlorite (0.32 N) containing 0.7 gm. caustic soda per litre, and after ten minutes 33.7% of the hypochlorite was found to have been used up. Immediately thereupon suilicient 'carbon dioxide was passed in to remove the free caustic soda in the form ,of sodium bicarbonate, with the result that after a further five minutes agitation, 91% of the hypochlorite was used up.. A

For the introduction of the carbon dioxide (eitheras such or as flue gases) or another destabilizer into the hjyiochlorite no the accomloo' y pai'iying' `.diagrammatic `drawings are illustrated, by way of example, two formsv of suitable apparatus. Fi re 1 re resents an apparatus suitable for t e introdiiction of carbon dioxide into the hypoclilorite.

Fi re 2 represents an apparatus suitable for t e introduction of car on dioxide or a y solution of another destabilizer together 1o` with hypochlorite solution and the oil to be ltreated into awasher. i

As illustrated in Figure 1, the carbon dioxide may be passed into the hypochlorite solution contained within asuitable receptacle a by a pipeb a portion of which is adapted to lie adjacent the bottom of 4the receptacle as at 4b1 and is perforated for the escape of gas into the solution andis closed bons with the said aqueous solution thus substantially de-stabilized, substantiallyas bed.-

BERNARD THOLE.

at the end. @The perforated pipe may be able arrangement of perforated piping or other means for'introducing the gas into the solution so that it may bubble through it.

Again, las illustrated in Figure 2, the carbon dioxide or other destabilizer may be supplied by a conduite to a pump d which l serves to draw su plies of 4the oil to be treated and of `the ypochlorite solution res ective'ly from the conduits e` and f, the de- .30 livery outlet of the'pum being connected by a conduit g with a was er h in which the reaction may be eiected', The carbon dioxide or other destabilizer is thus churned up by the ump and broi'i ht into intimate contact with the hypoc orite solution. 'The suction inlet ofthe pump may also be adapted to permit the um to drawiiipon the con- `:formed into a coil or be replaced by any suittents of the was ery wayv Qf\a conduit i,

andl thus to maintaincirculationand agitation of the said contents. The vsupplies of oil, hypochlorite .solution and carbon dioxide or other destabilizermay be vcontrolled b valves provided upon theres tive su p y conduits. Similarly, the -car on dioxi e 'through a by ass in to a pump serving for may be mtroduced-into the washer after the mixed therein. The

-or other destabilzer may be introduced the supply hypochlorite solution-or it i" hypochlorite solution and 'the oil have `been recedere `is the same whatever the] destabilizer used and the solu tion of the destabilizer may be'introduced d in the same way as the-carbon dioxide.

i -Itis preferred that the amount'of excess alkali be reduced during the treatment, but

a part of the excessmay bereduced immeto In ainetliod of relining'liquid hydrocarbons the steps of substantially destabilizing ankaqueoue solution of"a'hypochlorite cona slightaexcessloi valkali l by the addition into the solution of carbonio acid @M gas and washing the said liquidl hydrocar- 

